1. Field of the Invention
The present invention relates to a capacitor of an integrated circuit device and a method of manufacturing the same. More particularly, the present invention relates to a metal-insulator-metal capacitor of a semiconductor memory cell such as a dynamic random access memory cell, and a method of manufacturing the same, in which oxidation of a contact plug during deposition of a dielectric material having a high dielectric constant to form a dielectric layer is prevented.
2. Description of the Related Art
As a degree of integration of a semiconductor memory device, such as a DRAM cell increases, it becomes more difficult to obtain a sufficient capacitance due to a resulting decrease in size of individual memory cells.
Recently, various efforts have been made to obtain a sufficient capacitance from a limited cell area.
There are typically two methods to increase a cell capacitance. A first method is to use a material having a high dielectric constant as a dielectric layer of the capacitor. A second method is to increase an effective area of the cell using a hemisphere silicon grain (HSG) growing method.
As for the material having a high dielectric constant, a metal oxide layer comprised of Ta2O5, TaOxNy, Al2O3, (Ba, Sr)TiO3[BST], SrTiO3[ST], Pb(Zi, Ti)O3[PLZT], SBT, or like, is used instead of a silicon oxide layer or a nitride layer.
Even though the dielectric layer is formed by depositing Ta2O5 on a semiconductor substrate by a chemical vapor deposition (CVD) method, an oxygen vacancy where an oxygen bonding is absent is inevitably present in the dielectric layer. Therefore, a UV O3 treatment is typically performed to supplement the oxygen vacancy during the CVD process. Furthermore, the dielectric layer is crystallized by means of a heat treatment in an oxygen atmosphere to increase a dielectric constant after performing the deposition.
A storage node is oxidized through a reaction with oxygen when the dielectric layer comprised of Ta2O5 is subjected to the heat treatment in an oxygen atmosphere during or after the deposition thereof. Formation of an oxide layer through this oxidation process increases the thickness of the dielectric layer of the capacitor, thereby decreasing the dielectric constant, which results in a reduction in capacitance of the capacitor of the semiconductor memory cell.
Since the use of an existing polysilicon electrode is limited, a novel material for formation of an electrode and a novel structure of the electrode are required. As platinum (Pt) has a high reactivity to silicon, when platinum is used for formation of the electrode, a barrier layer is needed to insulate the platinum electrode from a contact plug comprised of polysilicon. Typically, titanium nitride or tantalum nitride is used as the barrier layer.
However, during or after deposition of a layer to form a lower electrode or a dielectric layer, a heat treatment is performed in an oxygen atmosphere to crystallize the lower electrode layer or the dielectric layer. During this heat treatment, oxygen diffuses along a boundary surface between a barrier layer and an insulation layer to reach a contact plug, resulting in oxidation of a surface portion of the contact plug. The oxidation of the contact plug decreases the capacitance of the capacitor of the semiconductor memory cell.
Hereinafter, a conventional capacitor of an integrated circuit device will be described.
FIG. 1 illustrates a sectional view showing a conventional concave type of a metal-insulator-metal capacitor of an integrated circuit device. FIG. 2 illustrates a sectional view showing a conventional convex type of a metal-insulator-metal capacitor of an integrated circuit device.
The concave type of the metal-insulator-metal capacitor of the integrated circuit device is formed in such a manner that a first insulation layer 12 is formed on a semiconductor substrate 10 and a contact plug 14 is formed in the first insulation layer 12. A diffusion barrier layer 16 comprised of a nitride material and a second insulation layer 18 are sequentially deposited on the contact plug 14. A through hole 20 is formed in the second insulation layer 18 and through the diffusion barrier layer 16. A barrier layer 22, a lower electrode layer 24, a dielectric layer 26 and an upper electrode layer 28 are subsequently formed in the through hole along a surface profile of the through hole 20.
The convex type of the metal-insulator-metal capacitor of the integrated circuit device is formed in such a manner that a first insulation layer 112 is formed on a semiconductor substrate 110 and a contact plug 114 is formed in the first insulation layer 112. A barrier layer 122 and a thick lower electrode layer 124 are integrated and subsequently formed on the contact plug 114. Then, the barrier layer 122 and the lower electrode layer 124 are patterned by a photolithography so that each node is defined. Subsequently, a dielectric layer 126 and an upper electrode layer 128 are sequentially stacked on the lower electrode 124.
In FIGS. 1 and 2, when the dielectric layers 26 and 126 are crystallized under an oxygen atmosphere, oxygen diffuses toward an upper portion of the contact plugs 14 and 114 along oxygen diffusion pathways 30 and 130 on a boundary surface between the barrier layers 22 and 122 and the insulation layers 12 and 112. As a result, the contact plugs 14 and 114 formed of polysilicon make contact with oxygen at the upper portion thereof to be oxidized and converted into silicon oxide layers 32 and 132, which act as an insulator. This increases a contact resistance between the lower electrode and the plug of the capacitor thereby decreasing reliability of the cell capacitor.
From FIGS. 1 and 2, it may be noted that since the convex type of the capacitor of the integrated circuit device has a shorter oxygen diffusion pathway 130 than the oxygen diffusion pathway 30 of the concave type of the capacitor of the integrated circuit device, the convex type of the capacitor of the integrated circuit device has a weaker structure. Accordingly, the plug of the convex type capacitor is more easily oxidized due to the diffusion of oxygen than the concave type capacitor of the integrated circuit device.
Furthermore, in the concave type metal-insulator-metal capacitor, the nitride layer 16 is disposed between the first insulation layer 12 and the second insulation layer 18 to prevent the diffusion of oxygen.
However, although the nitride layer acts to substantially reduce the oxidation of the upper portion of the plug, the nitride layer cannot completely prevent oxidation of the plug.
That is, it is difficult to prevent oxidation of the plug because the nitride layer as the diffusion barrier layer is not sufficiently dense, and a distance between the nitride layer and the upper portion of the plug is very short.
In order to solve the aforementioned problems, it is a feature of an embodiment of the present invention to provide a capacitor of an integrated circuit device capable of preventing oxidation of a contact plug, in which a diffusion barrier layer is formed in a pathway through which oxygen diffuses.
It is another feature of an embodiment of the present invention to provide an advantageous method of manufacturing the capacitor of an integrated circuit device described above.
In order to provide the first feature of the present invention, a capacitor of an integrated circuit device according to a first embodiment of the present invention is provided. A first insulation layer is formed on a semiconductor substrate, and a buried contact hole is formed therein. A buried contact plug is formed in the buried contact hole for filling a portion of the buried contact hole to a predetermined height. A diffusion barrier spacer is formed on the buried contact plug and on an inner side surface of an upper portion of the buried contact hole. On the first insulation layer, a second insulation layer is formed. The second insulation layer has a through hole having a diameter larger than that of the buried contact hole. Through the through hole, the diffusion barrier spacer and a top surface of the contact plug are exposed. A barrier layer is uniformly formed on an inner side surface of the through hole to a predetermined thickness and a lower electrode is uniformly formed on the barrier layer to a predetermined thickness. A dielectric layer is uniformly formed on the lower electrode and an upper surface of the second insulation layer to a predetermined thickness. On the dielectric layer, an upper electrode is uniformly formed to a predetermined thickness.
In the capacitor of the first embodiment of the present invention, the diffusion barrier spacer is preferably formed of Al2O3, which is denser than a nitride layer and preferably has a thickness of about 50 xc3x85 to 500 xc3x85.
According to the first embodiment of the present invention, the upper electrode and the lower electrode are preferably comprised of any one selected from the group consisting of Pt, Ru, Ir, RuOx, IrOx, and a mixture thereof. The barrier layer is preferably comprised of TiN, TiSiN or TaN. Also, the dielectric layer is preferably comprised of at least one selected from the group consisting of Ta2O5, TaOxNy, Al2O3, (Ba, Sr)TiO3[BST], SrTiO3[ST], Pb(Zi, Ti)O3[PLZT], SBT and a mixture thereof.
In particular, the capacitor of the integrated circuit device according to the first embodiment of the present invention may further include a diffusion barrier layer, preferably comprised of Al2O3, between the first insulation layer and the second insulation layer. Preferably, the diffusion barrier layer has a thickness of about 50 xc3x85 to 500 xc3x85.
In order to manufacture the capacitor according to the first embodiment of the present invention, a first method of manufacturing a capacitor of an integrated circuit device is provided as follows. First, a first insulation layer is formed on a semiconductor substrate. Then, a buried contact hole is formed in the first insulation layer. A portion of the buried contact hole is filled to a predetermined height to form a buried contact plug. A diffusion barrier layer having a predetermined thickness is uniformly formed on an upper surface of the first insulation layer, an inner side surface of an upper portion of the buried contact hole above the buried contact plug, and a top surface of the buried contact plug. An etching stop layer and a second insulation layer is formed on the diffusion barrier layer.
Then, the second insulation layer and the diffusion barrier layer are etched to form a through hole so that the top surface of the buried contact plug is exposed and a diffusion barrier spacer is formed on the inner side surface of the upper portion of the buried contact hole. The through hole has a larger diameter than that of the buried contact hole.
Subsequently, a barrier layer is uniformly formed on the top surface of the contact plug to a predetermined thickness. A lower electrode is uniformly formed on the barrier layer to a predetermined thickness and a dielectric layer is uniformly formed on the lower electrode and the upper surface of the second insulation layer to a predetermined thickness. Then, the dielectric layer is heat treated in an oxygen atmosphere in order to crystallize the dielectric layer. Next, an upper electrode is uniformly formed on the dielectric layer to a predetermined thickness.
Alternatively, a second method of manufacturing the capacitor according to the first embodiment of the present invention is provided as follows.
A first insulation layer is formed on a semiconductor substrate and then, a buried contact hole is formed in the first insulation layer. A buried contact plug is formed in the buried contact hole to fill a portion of the buried contact hole. Then, a diffusion barrier layer is uniformly formed on the first insulation layer, on the buried contact plug and on an inner side surface of an upper portion of the buried contact hole along a surface profile thereof, to a predetermined thickness. A second insulation layer is formed on the diffusion barrier layer. Then, the second insulation layer and the diffusion barrier layer are etched to form a through hole to expose a top surface of the buried contact plug and a diffusion barrier spacer on an inner side surface of the upper portion of the buried contact hole. The through hole has a larger diameter than that of the buried contact hole. After that, a barrier layer is uniformly formed to a predetermined thickness on a bottom and side surface of the through hole along a surface profile of the through hole. A lower electrode is uniformly formed on the barrier layer to a predetermined thickness and a dielectric layer is uniformly formed on the lower electrode and an upper surface of the second insulation layer to a predetermined thickness. Then, the dielectric layer is heat treated in an oxygen atmosphere to crystallize the dielectric layer. Next, an upper electrode is uniformly formed on the dielectric layer to a predetermined thickness.
Another feature of the present invention may be provided by a capacitor of an integrated circuit device according to a third embodiment of the present invention. The capacitor includes an insulation layer which is formed in a semiconductor substrate, the insulation layer having a buried contact hole formed therein and a buried contact plug filling a portion of the buried contact hole to a predetermined height. A diffusion barrier spacer is formed on the buried contact plug and on an inner side surface of an upper portion of the buried contact hole above the buried contact plug. A barrier layer is uniformly formed to a predetermined thickness on an upper surface of the insulation layer, the diffusion barrier spacer and the buried contact plug. Preferably, the diffusion barrier spacer is formed of Al2O3 and has a thickness of 50 xc3x85 to 500 xc3x85. A lower electrode is uniformly formed to a predetermined thickness on the barrier layer and a dielectric layer is uniformly formed on the lower electrode. Further, an upper electrode is uniformly formed on the dielectric layer to a predetermined thickness.
According to another aspect of the present invention, a method of manufacturing a capacitor of an integrated circuit according to the third embodiment of the present invention is provided as follows. An insulation layer is formed on a semiconductor substrate and a buried contact hole is formed in the insulation layer. Then, a buried contact plug is formed to fill a portion of the buried contact hole to a predetermined height. A diffusion barrier spacer is formed on an upper inner side surface of the buried contact hole. Then, a barrier layer is uniformly formed to a predetermined thickness on an upper surface of the insulation layer, a diffusion barrier spacer and a top surface of the contact plug. A lower electrode is uniformly formed on the barrier layer to a predetermined thickness and a dielectric layer is uniformly formed on the lower electrode to a predetermined thickness. Also, an upper electrode is uniformly formed on the dielectric layer to a predetermined thickness.